1. Field of the Invention
The present invention relates generally to filtering devices. In particular, the present invention relates to a renewable spin-on type filter having a high strength plastic housing.
2. Discussion of Background
Spin-on, twist-on type filters are used in numerous liquid and pneumatic applications throughout the agricultural, transportation, commercial and industrial markets. The housing or can for most spin-on disposable filters are manufactured from malleable materials, such as aluminum, by a deep-draw forming process. This technique limits the structural capabilities of current spin-on and twist-on type disposable products to the production capabilities of the metal forming industry and to the molecular characteristics of a limited number of specific malleable metals. Prior art disposable filters use stamped steel or cast cover plates to secure the housing or can to a mounting and distribution head assembly. This plate typically has a threaded center hole and is spot-welded and/or crimp-sealed to a deep drawn can. The purpose of the cover plate is to provide a mounting section that contains sufficient strength to allow operation of the filter at the required pressure rating. These prior art techniques for sealing and connecting the can to the plate, plus the structural limits of thin gauge malleable metals, restrict the application and uses of prior art spin-on, twist-on disposable filters. Recently, new high pressure, high burst strength disposable filter housings with burst pressure ratings in the 1000 psi range have been developed for some narrowly defined markets and applications. However, even these newer, high-strength filters remain applicationally limited because of their continued use of deep-drawn metal cans.
The filter media used in the prior art are usually paper products that are flexible and flimsy. As a result of their flexible and flimsy characteristics, these filters often are not properly secured in place within the housing or can during the assembly of the filter. By some accounts, 50% of current commercially available oil filters are defective and thus do not perform up to specification. Also, prior art paper filters often develop rips or tears during use. For example, if there is a spike in the pressure of the fluid being filtered, paper filters will often develop a rip through which unfiltered fluid flows. Such rips generally increase in size as a result of the rush of fluid flow there through. Such defects are not visible and unknown to the machine operator and the use of the filter continued for its normal use period during which improperly filtered oil is re-circulated through the machine or engine. Serious damage to the machine or engine can result. Once these disposable filters have been severed, they can no longer serve their purpose and should be replaced.
When conventional filters reach the end of their useful life, the filter is removed from the vehicle or machine and the remaining filtrate, usually oil, is drained and a new filter is installed. Thereafter, the filter should be compacted and disposed of in accordance with industry practice. However, often the used filter is disposed of in a way that it is eventually placed in a land fill. The impact on the environment from the disposal of used filters and oil is devastating to the environment. The enormity of this problem is realized when the variety of industrial and consumer applications that employ disposable filters, as well as the frequency with which these filters are replaced, is considered. The impact on the environment can be appreciated when it is realized that there are currently about 180,000,000 vehicles in the United States for which it is recommend that the filter and oil be changed every 3,000 miles. About 400,000,000 oil filters are manufactured in the U.S. each year, of which less than 25% are properly recycled. The remaining, which retain some oil, are disposed of and this used oil enters the environment. Even properly drained oil filters can retain up to 8 ounces of used oil. It is estimated that the result of proper recycling would result in the recovery of more than 17,000,000 gallons of oil. If properly processed, this oil could be reused.
Therefore, there exists a need for a twist-on filter that is renewable which would support and encourage the recycling of used oil and reduce environmental liability.
If an oil filter is not serviced, it can become clogged and the flow of incoming oil will be impeded and eventually completely stop from passing through the filtering media. When the filter becomes blocked with contaminates, fluid flow is restricted and diminished and the differential pressure across the filter element increases. As the volume of the flow diminishes, parts of the machine or engine that normally receive lubrication will receive inadequate lubrication. The typical lubrication systems for an internal combustion engine pump oil from a sump through a loop, splashing oil over and around moving engine parts, such as the valves and piston rods. The oil filter is a component through which the oil flows in this oil flow loop. Thus, if the oil filter becomes clogged, the flow of oil is impeded and lubrication becomes inadequate. However, the damage to an engine or machine will be less if the circulation of the contaminated oil is continued rather than allowing the circulation of oil to be stopped. Thus, it is important that a bypass be provided to allow the circulation of oil to continue when it cannot pass through the filter media. Also, when an engine that is in a cold environment is started, the viscosity of the crankcase oil is very high and resists being forced through the filter media. It is important, in such situations, that provisions are available to allow the oil to bypass the filter for a period while its temperature increases and its viscosity decreases. For these reasons, oil filters should have a bypass system to protect the engine in the event of a clogged filter. Bypass valves for oil filters are known. However, they are complicated, expensive and are not an integral part of the filter. There is a need for a filter device that has a simple mechanical bypass that is an integral part of the filter device and cannot be disconnected or tampered with.
A typical automotive poppet type bypass valve has a very limited surface area against which the liquid that is at an elevated pressure must react to cause the bypass valve to open. This renders the valve unreliable for its intended purpose. Also, the typical automotive poppet type bypass valve utilizes a compression spring to urge the valve closed. Compression springs are very vulnerable to premature fatigue failure. The filter of this invention has an infinite life and, thus, if the filter of this invention is provided, a built-in bypass valve should also have an infinite life. Another shortfall of the typical automotive type poppet bypass valve of the type that relies on a compression spring to return the valve to its closed position is that it is unlikely that full closure will be attained. Coil type compression springs are rounded on both ends and cannot be properly guided. As a result, compression springs take the path of least resistance when they expand. Furthermore, coil type compression springs do not exert an equal pressure over the length of their expansion and, thus, do not provide a uniform pressure on the poppet valve.
Accordingly, there is a need for a simple bypass valve that is built into a renewable filter that has an infinite life cycle to match the life cycle of the renewable filter. There is also a need for a filter having a bypass valve that has a relatively large surface against which the liquid at elevated pressure reacts to increase the reliability of the valve. Still further, there is a need for a filter having a bypass valve that does not rely upon a coil type compression spring to close the valve. There is also a need for a renewable filter having an integral bypass valve that, when fully open, has the capacity to bypass the full volume of the normal oil flow.